“While we are asserting patent claims of our own, we do so in response to Yahoo’s short-sighted decision to attack one of its partners and prioritize litigation over innovation,” said Ted Ullyot, Facebook’s general counsel, in a statement.

Facebook is seeking a dismissal of Yahoo’s suit, along with damages and legal fees.

Yahoo’s lawsuit, which it filed on March 12, accused the social network of infringing 10 patents for social networking, privacy settings and ads. At the time, Yahoo had already demanded that Facebook pay licensing fees for the use of its technology.

The lawsuits are just the latest in a string of patentwars companies are waging in the technology sector, and they come at important moments: Facebook is preparing for a highly anticipated initial public offering, and Yahoo announced today that it is firing 2,000 workers.